Electric signaling system



July 27, 1948. E. A. H. BowsHER ETAL '2,445,759

ELECTRIC SIGNALING SYSTEM Filed April 19, 1945 algal. A

2 Sheets-Sheet 1 July 27, l948- E. A. H. BowsHER ET AL 2,445,759

ELECTRIC SIGNALING ,SYSTEM Filed April 19, 1945 2 Sheets-Sheet 2 A TTOF/V Y Patented July 27, 14948 UNITED SIATES PATENT OFFICE 1 ELECTRIC SIGNALING SYSTEM l EdwardAlbert:Henry Bowsher, Harold Mountjoy Musehamp `1dAssis-Ionseca, and Hugh Jen- ...nings Ward London, England, assignors to standard 'lfelephones and Cables Limited, London,-England, aritish company -ApplicationApril A19, 19515, SerialNo. 589,245 In Great' Britain March 31, 1944 .Section LMPublic Law 6910, August 8, 1946 Patent expires March 31, 1964 6` Claims. A1 This invention .relates to electric signalling systems and more particularly to electric remote control` and supervisory systems.

i British patentA specification 514,991 `describes an electric vsignalling system inve n t ed by one; of n the present applicants in which. a control station and a selected. substation can .be connected together on, apar'ty line ,Common to a number of substations, and inwhichhold signals are continuously transmitted alternately in opqtiosite4 directions over .the party lineI so that the .controll plicable to a system which comprised a control station. and anumber ofparty-line substations, each station including asigna] sender land a'signal receiver. VWhen the system is at rest, communication between the control station, and any substation can be initiated by either of them. In the first case'the control sends out asignal'dstinctive of the one substation desired,v andthis signal, although received by `alljthe substations, is effective only atthat one.' Further identity checking and'like signals may be exchanged between the two interconnectedl stations; but eventuallythe substationl will send back signals descriptive Aof 'the condition of each apparatus unit, e. g. circuit breaker, in the substation. f In the second case, some occurrence in an apparatus unit in any one substation, e. g. the tripping of a circuit breaker, automatically causes the substation to send asignalto the control, and again,v

with or without a further exchange of signals, the substation will send signals descriptive of the condition ofthe apparatus units. lFurthermore, this same party-line is used for the sending of control signals from the contro-lstation to any one apparatus unit in any one substation, for

Vthe purpose of changing or confirming its conhowever,` the engineerY atfthe ,control station wishes to effect acertain control at the substation, he causes the pulses from the control sta- .tion to berfmodiecl. `In the prior case above re- L ferred vto this `modificationl consisted of. a length- V ening of a single pulse; in the present invention i on the other hand means are provided so .that at least two consecutive longpulses must bevreceived to effectthe control.

. yOne. of the advantages of Athe arrangement in accordance with the present invention is 4that it Amakes theo-peration of a signalling system as del scribedmore reliable and less subject .to upset l from extraneous causes.

Thus where lthe conl. trol signal consists of one long pulse only, it might kbe simulatedby lthe application of a battery to lthe line .or ythe induction of .an electromotive force therein in any accidental manner; the present invention therefore uses a pluralityof long ipulses asthe control signal and thev control cir- `cuit is, designed to respond only to suchsignals. .-Another. advantage of the arrangement in accordance with the presentinvention is that it enables the engineer at the control station to maintain .thecontrol for as long as -he deems it necessary. `The apparatus to be controlled, such has become effective.

The description that follows relates to the accompanying drawing, in which:

Fig. l-shows the circuit of the equipment at the control station for the control and supervision and .of the several apparatus units at a substation;

Fig. 2 shows the circuit of the corresponding equipment at a substation.

Y ing-the number of relay armature contacts associated with'that relay, the relay armature contacts being designated by corresponding small reference letters and a number indicating the particularcontact involved.` For example, `in 2 relay SAS has seven contacts and 'is shown asY SAS/1 and these contacts are designated sasl, sasZ, m53, sasil, sas5, sas6, sas`l -These contacts are not s hown adjacent to the relay tonwhich 'they belong, but are arranged in the circuits controlled by them, thus considerably simplifying-the `drawing and facilitating the tracing of GENERAL DESCRIPTION The control station shown in Fig. 1 and a plurality of substations like that shown in Fig. 2 are connected to a common two-wire line Ll, L2.

An individual connection between the control station and any one substation can be set up to the exclusion of all the other substations and can be maintained so long as necessary; this setting up can be initiated either from the control station or from the substation. At CSC in the control station, and SSC in the substation are indicated known selection circuits by means of which signals can be sent and receivedfor the purpose of selecting firstly a particular substation from among those on the common line and secondly a particular apparatus unit from among those in the particular substation, the latter selection involving a setting of the stepping switches indicated by the wipers SPCI and SPCZ in the control station and SPSl, SPS2, and SPSS in the substation. Each selection circuit includes a signal sender and a signal receiver so interlocked that the sender cannot function whilst signals are incoming to its associated receiver. Once an individual connection has been set up between the control station and a particular substation, that connection is maintained and other stations excluded by the continuous exchange of signals between the two stations over the line in the manner disclosed in the patent specification No. 514,991 above referred to. The signals from the control station are single short negative pulses, while the signals from the substation are single short pulses that are positive or negative according as the particular circuit breaker is at the time closed or open. Thus the polarity of the signals sent from the substation during shuttlecocking furnishes a supervisory indication at the control station of the condition of the selected circuit breaker because the appropriate indicating lamp will be lit at the control station.

When the engineer at the control station desires to change-over the circuit-breaker, he depresses the close key CK or the trip key TK, as

the case may be. Then, so long as the key is held down, the short negative pulses from the control station are replaced by long pulses that are either positive or negative according as the control is that of closing or opening. The substation pulses continue short, but will be reversed in polarity as soon as the breaker has actually changed over.

Before describing the detail circuits, the following brief description of the sequence of operations will assist in a better understanding of the invention and of the novel features involved. Thus, after selection of thev desired substation and the particular circuit breaker at the substation, the following sequence occurs: Relays PSC at control and PSS at substation operate and at contacts pscl, psc2, and pssl, pssZ switch the line Ll, L2 from the selection circuits CSC and SSC to the polarised pulsing arrangements. Relay SA at the control station operates momentarily and at contacts sal, sa2 connects negative feed line to line Ll, the negative pulse thus transmitted causing operation of polarised relay SN at substation. This operates slow release relay PGS-and when SN releases at cessation of feed 4controlled bySA, relay SAS operatesand at contacts sasl, sasZ switches the line Ll, L2 at the substation from the polarised relays to the feed. The pulse thus transmitted from the substation, Which is negative if the circuit breaker is in the tripped position, and positive if the circuit breaker is closed, operates polarised relay CN or CP at the control station, thus causing operation of slow release relay PGC and supervisory relay OL which controls the Red and Green indicating lamps, the green lamp indicating that the circuit breaker is tripped and the red lamp that it is closed. Operation of PGC causes operation of relay SA as soon as the polarised relay CN or CPfalls olf at the cessation of the pulse from the substation, and relay SA at its contacts sal, cd2 again connects negative feed to the line and the same sequence of operations is repeated. It will thus lbe seen that relay SA at the control station and relay SAS at the substation are the relays which control the transmission of shuttlecock ipulses between the control station and a selected substation. These relays also control the long control pulses as will be seen later.

When the engineer at the control station wishes to close a circuit breaker at the substation, he

presses his close key CK and this has thev effect of energising relays CR and TL. Relay CR. at contacts crl, crZ changes the feed on the line to positive, and relay TL at contact fZl prelpares a locking circuit for relay SA so that this relay will be held operated to send a long pulse, and as contact cl has connected positive potential to line Ll, a long positive pulse is sent to the substation. The duration of this pulse is determined by the successive release times of the two slow-release relays PGC and PGL as PGL is controlled by PGC and PGL has a contact pgll in the locking circuit of SA and thus SA is maintained operated until both PGC and PGL release.

The effect of this long positive pulse at the substation is to operate polarised relay SP and hold it operated for the duration of the pulse thus preventing relay SAS from operating quickly as it did for the shuttlecock pulsing and this allows the slow release relay SAR, which is controlled by SAS, to release and allow relays X and Y to operate. The operation of these relays causes the operation of relays CRS and LP which at contacts crsl and Z108 prepare the operating circuit for the close magnet CC for the circuit breaker. When the long pulse ceases, polarised relay SP releases and allows SAS to operate, and this, as previously described, sends a short negative 4pulse lto the control station which will be indicated by the lighting of the green lamp as the circuit breaker is still tripped. It will be observed that the effect of the first long pulse at the substation was merely to prepare the circuit for the close magnet CC but this magnet did not operate at this time as its circuit was broken at .'L'l and yl. It will also be observed that operation of relay SAS reoperated slow release relay SAR with the result that relay X released at sa13. At the cessation of the negative pulse from the substation, polarised relay CN at the control station falls off and relay SA reoperates. As the close key CK is still depressed another long positive pulse will be sent. Relays CRS and LP remain operated over locking circuits, so that this time when slow release relay SAR releases, it will cause the With relays X and Y now released and CRS and 13B still operated, the circuit for fclosemagnet f CC is completed over wiper SPSS, 'crsl up, yl, ml, lp upvvv to positive batter. `Thecircuit breaker "closesV and operates `the lfbreaker contact -IC to vclose the contacts CI," C2, thus operatingrelay `JB over the wiper SPSI. l Rel'ayJB-operates re- Alay PP which at contacts` ppl- 'andpioZv vreverses the feed and the next pulse from the'lsubstation willlbe positive. A positive pulse at the Acontrol `:station operates polarised relay-CP which oper-f' ates Athe latching winding L of relay OL :to light the red lamp. These operations are repeated -automatically as long as the closed key CK: is `ldepres'sed,but the lighting offthe red lamp indicates tothe control engineer that the circuit breakerat' the :substation is closed, andhe would then release vthe key.

Operation of the tripA key TK results in a similar series of operations but in this case Along '-ne'gative control'pulses will be sent as relayf CR.H

y"does Inot operate. At the substation polarised l'relay'SNi operates, and instead of relay CRS, the relay- TLS-will operate with LP, and thus the oper- `atingcir-cuit for the trip magnet-,TC is pref'par'ed at tls! and thisma'gnet will operate ini iftheicircuit over wiper SPSZ, tl'slup, yl,` crI; Zp up when relays X and Y release aspreviously described. Breaker contact IC opens the `circuit of --relay =JB which releases relay PP with the result that the supervisory pulse from the substationl will be negative. This causes operation of polaris'edrelay CN at the control station with the result that the unlatching winding U- oi the super- 'visory relay O-L is operated and the -green f lamp -is lit, thus indicating that the circuit breaker?" h'as'trizpped.

DETAILED DESCRIPTION Setting up and holding a connection The engineer at the control station, desiring'w *set up a connection toV a particular substation, "transmits a set of impulses from CSC over the party line Ll, L2, to the receiving `equipments in theselectioncircuits SSC at all the substations. `fhis-set of-impulses selects the' yonesubstation Honly. Then a further set ci impulses is transmitted from CSC,this time being determined by the setting of switch wipers SPCI and SPC2- and having the purpose oi selecting a particular piece of apparatusfsuch as a circuit-breaker in the said substation. The switch wipers SPS I-SPS3 inthe i substation circuit SSC are thus positioned on an f'outlet unique to that piece of apparatus. Provision may or may not be made tosend back to the control station a signal confirmatory of the acltual :position of the selector wipers' SPSI--SPS3;

4in any case at the end of such selection signal the selection circuits CSC at the controlstation and -f SSC at* the substation will cause the operationof their respective relays PSC and PSS.

At the same time in the control station the selection circuit CSC applies a short-circuit across contacts pgcl as indicated `by the dotted line `A sothat as a result of the operation of relay PSC," relay SA is operatedini a circuit:V positiveybattery psci up, cnl, cpl, the CSC shunt A, winding of relay, SA to negative battery. The-contacts sal and-str2 are arranged togive alternative 'connections of the line LI, L2, either to a battery v feed for sending signals'to the substation, or to a `'pairiof relays CN and CP for receiving similar signals 'from the substation. Thus whenSAoperates, a feed is lapplied tothe" line fromil'negative fl over resistance YC, contactsl cr I ,Afs'a I- iup, fpsclllup,

T6 to Wire LI; and -ffromffpositive over: contactsc, 1sa2. up,'i-psc21up to wire L2. @A feed 'of thiswpolarwity,.xnegative on LI and: positive :on L2,islfor convenience, designated`- a negative deed, whereas 5 positive on LI and negati-veen Lzis designated as positive Steed. v'."Il'ieioperating"circuit vfor relay SA.isr.1mair-1taind `byffthe shunt' A lin CSC-fior: a short period only, after which SA releasesfand lt'akes Vlthennegative. lfeeds 'offf the :line by :opening lvthepontacts' satandlsa. 1

sAt" 'the substation, *FigJ 2,'the feed.. isiv applied iitoi :.ther.` ioppostelyf-po1arised relay bridge .fSN, I SP soverthefop'erated contacts:y pssl: and .pssZ, .it be- 'ing remembered lthat' relay: PSS` 'operated at the end of :the substation :selection fsignal. i The feed -being negative it causes relay." SN adoperate', in turn operating slowrelease relay PGS: from positive" 4'battery .pss 8..; up; Isn I: up; left-hand 1 winding Voi PGS. ""W'hen the' feedfisutaken; off due .tolthe 20. release 'of-relaySAiin lthe'.l control" station; i'relay SN' releases; and' relay: SAS. operates; from positive battery 'over-pssi uppsn I ,'1 rsp I pas I up,l :lp 5, Winding of relay SAS to negative. Contacts lsasl up and sasl-up, apply. tothe` linea feed which may be either positive or negative as will appear below. At the sax-netimethe -relea'seof SN-has opened' the operating* vcircuit""ofuelay TGS; and this relay slowly releases, its` `delay-pericci-determining "the duration fof the Vfeed -to the? line f because-fthe'"operating circuit for relay `SAS over whose'contacts sas I and'f'sasZ t-he feed-is applied, inclu'desithe contact-pdsl'ofrelay PGS.

The control'station' responds to? the feed applied -att he`V 'substation with-i the,Z operation lof polarisedrelay GNo CP; according tothe feed polarity, vin either caseroperatingf'the 'slow-release relay PGO: 'from batterypsc3 up, andfeither 1cnlcup, f Vor 'cpl up tothe 'right or left hand Iwinding of relayPGC. Whenltheffeedristaken `oil? the line by the release fof -relaysPGS andfSAS '(Fig. 2), sot'h'atCN (OrCP) releases; relaySA operates: battery p`s`c3V up,l ycn I cpiy-pg'cl up, winding SA; the operation of relaySAi disconnects the'polarsed relay bridge CN CP from the line at contacts sal and sa2, and re-applies negative mfeedas betorefdescribed. At. the saine timethe Mrelease of 'CN :(or CP)f I has-'opened the operating :circui-t'of relay PGC, and this relay releases slowly, y fits Vdelay period'fdetermining the duration ofthe .feedlto the line lby virtue fof its control :of -relay This-cycle of operationgconsisting 4of a` pulse in l i-e'achf direction; :and repeating itself vuntil release :zof eitherwrelay'PSS at Athesubstation-or PSCl at ;.the control station, iis the -.shuttlecockingf `disclosed. in our labove-mentioned :patentgspecifica- -tion'Y `'and fisv lthe means f whereby 'theA line'.A isy Vheld byV 4'the' one: substation to" the exclusion :of l the wothers. 1

Utilisation o! thefsubstatton signals'for supervision f'It has been stated above thatl those shuttlecock .signals originating. atl the substation might ybefof either polarity. This polarity depends uponfthe I'fc'onditionof the circuitA breaker 'orffother vappa- '.ratus' that `has vbeen'selectedbythe positioning l of "sWitcl'rSPS As ,"shown' in Fig. 2r the 'circuit 'breakerselected' has a pair fof. auxiliary contacts rcI: and "c2rfwhi'ch' Iare` closedoropenedby the .varrnaturefIC. assoca'tedfwith the circuit breaker, e which' is not shownl'inithe drawing; `.according-to Htheficirc'it 'breaker condition; One ofthe conl '-tacts clI is connected tothe-:appropriate A contact L7 5.-"=in`rthe1bank fof the-selectorI associated with wiper nest SA operates.

. SPSl. The wiper SPSl leads to the relay JB, via -contact pssl and relayJB is thus operated or notoperated by armature IC according to the breaker condition. Relay PP follows the movements of JB, operating or releasing as that relay operates or releases contact i172 but only when relay SAS is released to close the` back contact sasl.

At the control station, Where either relay CN or CP responds, positive potential is applied either to wiper SPCl lor SPCZ of the selector over the contact cul or cpl respectively, To the banks yof the selector associated with these wipers, on

outlets corresponding to the breakers at the substation, are connected the latchin-g and unlatching` windings marked L and U respectively of mechanically latching relay OL. Thus the latching relay OL follows the movement of the corre- .,sponding circuit breaker, and its contacts oZl lightsl one or other of a pair of lamps marked ,fgreeni `and .red,` respectively to give a visual indication on the control board of the breaker condition.

Circuit breaker control Before proceeding with the description of the operation of closing a breaker, it should be pointed out that when SAS and SA rst operated at the substation and control station respectively, slow release relays SAR and SR were also operated over obvious circuits including contacts sasl and sad respectively. At the substation this resulted in operation of relay X; from positive battery, pss up, sar3 up, g4, Zpl left hand winding of relay, X to negative; and at the control station in the maintenance of relay PSC over srl. At the control station also, the first operation of relay PGC brought up the slow-release relay PGL over contact pgcZ which prepared a locking circuit for relay SA over contact pgll.

When the selected breaker is to be closed or tripped the appropriate non-locking close or trip key CK or TK is depressed.

Closing a breaker Key CK is depressed and when relay SA ilrst releases at pgcl as previously described the relay CR operates; psc4 up, sa, CK closed, CR; and brings up relay TL over contact cr3. Relay CR by its contacts crl and cr2 reverses the polarity of the feed that will be offered to the line when Contacts tll .complete the preparation of the locking circuit of relay SA,

.so that when this relay next-operates it locks;

psc3 up, cul, cpl, p r/Zl up, tZl up, sa3 up, SA; thus maintaining the feed to theline beyond the short time pulses previously described for shuttlecocking. Relay PGC is meanwhile releasing slowly and finally falls olf, thus starting the slow release of relay PGL whose contact pgll is in the locking circuit of SA. Throughout the successive release times of PGC and PGL relay SA remains up, so that the feed to the line is not only of positive polarity but is of lengthened duration.

At the substation polarised relay SP operates in response to the long positive pulse, and relay SAS is prevented, at contact spl up from operating for a longer time than hitherto, suiciently long for slow-release relay SAR to drop olf and operate relay X in the circuit from positive, pss5, sar3, lpl to X. Operation of relay X closes the circuit for relay Y at m5 and relay Y operates in the circuit; pss5 up, sar3, m5 up, Y. With both relay X and relay Y now operated relays LP and CRS operate; pss6 up, snl, spl up," 'up, ya up, left-hand winding of LP, or tls2, left hand winding of CRS. These relays lock in the following circuit; middle winding of LP, Zpl up, sar2, pssl; and right-hand winding of CRS, crs3 up, lpl up. With the operation of CRS a circuit is prepared for the close contactor magnet CC over contact crsl.

Ultimately, when the positive feed is taken off the line, relay SP releases, and relay SAS operates in the following circuit; pssS up, sul, spl, pgsl up sarl, SAS; relay SAR operates over sas'l up. Operation of relay SAR releases relay X at contact sar3 up but leaves Y up. The operation of SAS applies negative feed to the line over contacts sasl and sasZ for a short period determined, as before, by the release time of PGS.

At the control station relay CN responds to the negative feed, bringing up relays PGC and PGL as before, and energising the unlatching winding U of relay OL via SPCl wiper and bank. Contacts oll in the unlatched position light the green lamp. At the end of the feed from the substation, relay CN releases and, relay SA operates and locks, applying a positive feed to the line for a lengthened period determined as before by the slow-release times of relays PGC and PGL in succession.

At the substation, as before, relay SAS remains inoperative during the long positive pulse, so that again SAR releases. This time relay Y releases, and completes a circuit to the closing contactor CC; lp8 up, l, yl, crsl up, SPSS, CC.

This cycle of operations, consisting of short pulses from the substation and long positive pulses from the control station, will be repeated so long as the close key CK is held down at the control station. At the substation relay LP will hold, and will prevent the repeated operation and release of SAR from operating relay X which in turn keeps relay Y unoperated; also 4contacts lpl up will maintain relay CRS operated and this in turn maintains the operating circuit for the closing contactor CC.

When the circuit-breakercloses, the armature IC closes the contacts cl and c2 and relay JB operates in an obvious circuit over SPSl and pss up. Upon the next release of SAS therefore, relay PP operates and locks over 7b2 up, reversing at contacts ppl and pp2 the polarity of the subsequent pulses from the substation. This reversal of polarity is effective at the control station to operate relay CP instead of CN, thus energising the latching Winding L of the relay OL over SPC2, cpl up, cul, psc3 up and lighting the red lamp instead of the green at contact oll.

negative pulses, but now relay SAS is held inoperative for a time insuicient to cause the release of slow release relay SAR, so that at the end of the first short pulse relay SAS is unable to operate in the usual way owing to the break in its circuit at sarl up. Also relay LP releases,

. its one holding. circuit being opened at sul, and

9": its. 0the.r fholdiner-circuit. opened at fsar2 up. S1186,A and pgslup. Relay.CRS yreleases at Zpl., releas. ingthecontactor CC at crsl.v Theoperating.cir-l cuit of SAS Ais. closed at ,Zp5, and .the normal shuttlecock., Working.. is restored as. described above.

Tripping/,a breaker Considering now the alternative control,` that ofA trippingva-breakerg this is `to be. doneby Adepressing-.the-trip key The operations are then similar to thosealready described,A eXcept that the.` polarity of-fthe lengthened pulsessent from thecontrol station` is negative,` relay CR not.

At the control station, relay CNrespondsener.-v

gising theA un-latching WindngU of relayI OL over cul, and lighting the green lamp. instead of thQ-:Ieds

It .-Will; thus bev seen that long .pulses ,from the control; stati-on; persist sov` long as the control key GK1OI\ ,-T I E is @held down andy -that the. `eiect .of thisatthe substationis to maintainfthecontactor magnet C.C orf-TCpoperated similarlyl.-v Thusthe contacter 'magnet can Ybe held 1 operated.. for.. a sulciently-flong time to-fallow. for the slowestoperatingpiece-,of y apparatus `controlled .thereby topper-ate.:I The short pulsesfromthe substationat :all times indicatethe positionof. 4the breaker, and -thusrgivep-the. engineer positivel and instant information enabling him to determine quite Ycer-f tainlyhow long tohold. the key down. ,y

It V,will be` noted-also. that, once. operated,`. relay JB cannotrelease until both, relayPP and relay SAS ,are.,operated; and. that PPl cannot operate or, release Whi1e. relay SAS is operated because inthe one case its operating circuit .over i122 4is brokenatsasll iup,A and in the other case its locking.. circuit iS. ,maintained over, ppji and sas4 up. Thus,if., th e breakeris closed kon to.a fault and immediately trips, relay JBI operatesas previously described @and locks until the next'operation of SAS, while relay PP, having already operated over ibzup, when SAS was unoperated, is held operated in its lockingcircuit over -ppll until SAS releases@ The pulse sentiat this time is positive, indicating the closed conditionasofthat provided thebreaker ihas @closed itsK auxiliarypcontacts cl and c2 by armaturefIQjy for no 'matter how short a period, a closed indication pulsev'of normal duration is sent back to the control station.

With both .PP anclSAS operated the locking circuit of relay JB is opened at pp3 and sas3 and, if. thebreaker has tripped, JB releases as` its lower Winding circuit is broken at the `auxiliary con.. tacts cl and c2. When next SAS restores, PP also releasesat v7b2 so-that .the negative feed circuit is prepared at ppl and pp2, and subsequent pulsesftransmitted by SAS V,arefoi negative polar:- itytindicatingpthe open condition-of thebreaker. Thus theqengineer is clearly` informed ethat the breaker was closed on to a fault and tripped immediately.

Incomplete control operation Thetperiod during .Whiolrfthepulses from;A the lll 1'0r control station; are. lengthened, is governed -by thetime. forwhich .the Close. key y.or VTrip key` is depressed., If`y the. key is depressedv for a -peri0d suflicientonly for. onellongrpulse to betrans.- mitted, the subsequent :short .pulses reset theidis.- criminating.. relays. at the substation `as follows;

The single long .pulseresultsinthe operation of, relays Y, LRand-CRS .(or'ILS), and, at the terminationoithis pulseyrelease of. relayX vas, previously described..

The complete control can only ,be ellected` by therelease of relay. Y while relays rLP. and CRS (or,` TLS) y remain Voperatech,which conditionf.. is achievednormally .by the, releaseof relay SARton thesecond longpulse.l` In this .case as thekeyK or `'Ilhlassbeeri. releasedlthesecond and followf ing pulsesare replacedbyshort pulses, andslow. release relay SAR does not release, so that. relay S.A S is unable to .Oper-.ate in .theusual may, at the termination of.` the `long pulse, owing to thee break in its` circuit at sarl up.. Alsorelay LP.releases,.its one, holding.. circuit. being opened.,at .SPI (or SNl.) and its other` holding circuit openedat sar..2 11p,.sast, and pgsZ up. Relay CRS (orTLS). releases atlpl and relay-,Y releases at 1p1.. Relay X` now operates .over itsorgnal.operatingcircuit 20ss,5,. sa13 ,and` 1pm-.and thewholecircuit isref, turned to the-normal shuttlecockr; condition..

Interfering long pulse If an interferingalong pulse -is imposed -onr the line from-someY external lsource this results; in releasing-` relay SR-at the 'control station andl relay SARr at the substation ,y because the appropriate polarised relays will befoperated -and prevent the shuttlecockfrelays SA' anda-.SAS fromv operating normal-ly; `Release-of- SR ,causesrelay #PSC to release,breaking downj theshuttlecock circuit at the control station `because the line isdiscon nected at ps e landfpscz fromV the -polarised relays.

At lthe substation thelong pulse results 3 ini-the operati-oni of relays X; and Y, relay and nrelay CRS (or TLS) 1 as ldescribedf, abovey and at :the terminatiOno-the pulse, ashor-t pulse is'lsentto the. control station in. ,theqnormal manner.` In this.case,l1owever,. as 4:thefcorrtrol shuttlecock cir cuits aredisconnected;v the'pulse has lno eiect, and. no. further Y,pulses taresent tok the substation. Thus .PGS `remains ..unoperated and .relay l PSS releases slowly,l disconnecting. the substation shuttlecockcircuit at .contacts pssl .and rss2, and reconnecting the selection. circuit to. .theA line.

What isclaimed. is:

l.. Inyaremote.controland supervisory system comprising a; control station` and4 a. substation 0n a party1 line, Wthmeans for'the transmissionof. electric.pu1sesof. short duration alternately from the control station to, ,the substation and. .from thesubstation. to .the control, station, and for. operating .acont rol.magnet. at the. substation. by the transmissionoof an electric pulse of, longer duratiom the. combination. with. said, control. mage net of. a., circuitomprsing. ,a .plurality` of relay contacts, apluralitypf relaysior controlling said Contacts.. relaymeans controlled. by said impulses. and. .havnetcontaots arranged. .to .prevent/operaie tion of. saidplurality .ofl` .relays during, receipt of impulsesof short duration, said relay means being Veiectivepn,receipt of an impulse. of llong durationtocause operation of said plurality o relaysto close certainhof said. relay contacts in the control, magnet circuit, means operative on cessationof said pulse of long *duration to transmit` a short ,supervisory pulse tothe control station, means atthe control .station operatedbysaid supervisory pulse to cause operation of an indicating device and operative on cessation of said supervisory pulse to cause the transmission of a second pulse of long duration, means at the substation responsive to said second pulse to cause said plurality of relays to close all the relay contacts in said control Ymagnet circuit, means controlled by the operation of said control magnet to change the nature of the next supervisory pulse to be transmitted from the substation, means operative on cessation of said second pulse to transmit said supervisory pulse to operate said indicating device, and manually operable means at the control station to cause the transmission of a further pulse of long duration if the said indicating device operated by said supervisory signal indicates that the required operation has not been eiected.

2.`Aremote controland supervisory system according to claim 1, wherein said plurality of relays includes two pairs of relays, each relay of each pair having a contact in the control magnet circuit,v and wherein contacts of one pair of relays control the operation of the relays in the other pair, and wherein said relay means controlled byv the pulses causes operation of said rst pair of relays on receipt of` a first pulse of long duration to cause successive operation of said relays of the other pair to close said contacts in the control magnet circuit, said relay means operating on cessation of said pulse to release one of said relays of. thej first pair to close its contact in the control magnet circuit andre-operating on receipt of a second pulse of long duration to release the other relay oi" the pair to close its contact in the control magnet circuit, whereby the control magnet circuit Vis closed only after receipt of at least two pulses of long duration to operate said relay pairs in sequence.

3. -A -remote control and supervisory system according to claim 1, wherein the transmission of pulses from the control station is controlled by a relay device arranged in a circuit including contacts of aslow'release relay and an auxiliary lockingcircuit including a contact operated by a controlkey, and contacts of a second slow release relaycontrolled by said rst slow release relay, whereby said relay controls the transmission of pulses ofy long or short duration, depending on whether the control key is operated or unoperated to close or open said locking circuit, and whereby the duration of each pulse of short duration is controlled by the release time of said rst slow release relay, whereas the duration of each pulse ofi long duration is controlled by the successive release times of both said slow release relays.

4. Aremote control and supervisory system according to claim 1, wherein the transmission of pulses from the control station is controlled by a relay device under control of pulses received from the substation and wherein said relay device actuates a slow release relay, adapted to remain energised during short releases of said relay device,said slow release relay being adapted to cause release oi' the control station circuit when de-energised as the result of an interfering pulse of long'duration being imposed on the line.

5. In a remote control and supervisory system comprising a control station and a substation on a pa'rty line, with Fmeans for the transmission of electric pulses of short duration alternately from the control station' to the substation and from the substation to the control station, and for operatingv a control magnet at the substation by the transmission of an electric pulse of longer dura- Number` tion, the combination with said control magnet of a circuit comprising a plurality of relay contacts, a' plurality of relays for controlling said contacts, relay means controlled by said impulses andhaving contacts arranged to prevent operation of said plurality of relaysduring receipt of impulses of short duration, said relay means being eiective on receipt of an impulseof long duration to cause operation of said plurality of relays to close certainof said relay contacts in the control magnet circuit, means operative on cessation of said pulse of long duration to transmit a short supervisory pulse to the control station, means at the control station operated by said supervisory pulse to cause operation of an indicating device and operative onc'essation of said supervisory pulse to cause the transmission of a second pulse of long duration, means at the substation responsive to said second pulse to cause said plurality of relays to close all the relay contacts in said control magnet circuit, means controlled by the operation of said control magnet to change the nature of the next supervisory pulse to be transmitted from the substation, and means operative-on cessation vof said vsecond pulse to transmit'saidsupervisory pulse to operate said indicating device.

6. In a remote control and supervisory system comprising a control station and a substation on a partyv line, with meansA for the transmissionI of electric pulsesof short duration alternately from the control station tothe substation and from the substation to the control station, and for operating a control magnet at the substation by the transmission of an electric pulse of longer duration, the combination with said control magnet of means effective onreceipt of an impulse of long duration toconditionvthe vcontrol magnet circuit, meansoperative on cessation of said pulse of long duration to transmit a short supervisory pulse to the control station,rmeans at the control station operated by said supervisory pulse to cause operation of an indicatingdevice and operative on cessationrof said supervisory pulse to cause the transmission of a second pulse of long duration, means at the substation responsive to said second pulse to close said `control magnet circuit, means controlled by the operation of said control magnet to change the .nature of the next supervisory pulse to be transmitted from the substation, and means operative on cessation of said secohdpulse to transmit said supervisory pulse to operate said indicating device.

EDWARD ALBERT HENRY BOW- sHER.

HAROLD MoUNTJoY-MUSCHAMP DAssIs-EoNsECA.

HUGH JENNINGS WARD.V

REFERENCES CITED '-Iheffollowing references are of .record in the le of this patent:

y Name Date 2,276,646" Boswau Mar. 17, 1942 2,344,231 Burns l Mar. 14,1944' FOREIGN PATENTS Number i Country i l y Date 514,991 Great Britain f Nov. 23, 1939 

